1. Field
Aspects of the present invention generally relate to an image forming apparatus such as a copying machine or a printer which includes a fixing unit.
2. Description of the Related Art
In recent years, there are image forming apparatuses such as the copying machine and the printer which operate at higher speed. Further, there is an increase in color image forming apparatuses, so that power consumption is increasing in portions other than the fixing unit of such image forming apparatuses. On the other hand, the maximum current which can be supplied from a commercial power supply to the image forming apparatus is restricted by a standard. As a result, the power which can be allocated to the fixing unit is decreasing. To solve such a problem, Japanese Patent Application Laid-Open No. 2007-108297 discusses setting timing at which a recording material starts to be conveyed based on warm-up state of the fixing unit, a voltage state of power supply, and an environmental temperature when forming an image. A fixing failure can thus be prevented, and a first print output time (FPOT) can be shortened.
However, if the image forming apparatus operates with an option external device such as an option sheet discharge device or an image scanner connected thereto, the power suppliable to the fixing unit is further reduced. To solve such a problem, when the option external device is connected to the image forming apparatus, the power to be allocated to the fixing unit is previously reduced by an amount of the power required by such an option device to operate. However, if the power to be supplied to the fixing unit is reduced, it becomes necessary to increase a warm-up time of the fixing unit to maintain fixing performance. In such a case, the FPOT becomes long.